When producing video, audio is important. Very important. If you’re just starting out, make sure to spend as much time learning about how to get good audio as you do on video. To that end, I wanted to offer five audio-related facts I think every filmmakers/videographer should know. These aren’t necessarily the most important. There just some key points that are very useful to have tucked away in your brain.
Cable Types. As I mentioned in my “Live Event Filmmaker Survival Guide,” it’s important to have various types of audio cables so that you can handle every occasion. The most common ones you’re most likely to encounter are XLR, quarter-inch and RCA.
XLR connections are the ones most desired by professional filmmakers and videographers. One key reason is because most XLR cables are “balanced.” Without getting too technical, that simply means that the cable is constructed in a way to reduce or eliminate electromagnetic interference. Longer cables are particularly susceptible to such interference. Quarter-inch cables are popular with many DJ or portable audio systems. You’ll recognize RCA cables as the ones connected to your old VCR or game consoles. Rarely have I been in a situation where I needed to use an RCA connection for recording audio.
Microphone Types. You could write an entire blog post on the topic of microphones (scratch that. You could write an entire book). It’s not the scope of this blog post to get into the specifics of each. I just want to make you aware of what’s out there and give you easy access to find out the details.
There are wireless mics and wired mics. There are shotgun mics, lavalier (aka “lav”) mics, handheld and PZM mics. You got your omni-directional (picks up audio from all around the mic), uni-directional (picks up audio from directly in front of the mic), bi-directional (picks up audio from front and back). You got your cardioid, hypercardioid and your supercardioid (cardioid means “heart-shaped” and describes the pick-up pattern of the mic. Handheld mics are usually cardioid. Shotgun mics are typically hyper or supercardioid because they eliminate most of the audio coming from the sides). You got mics with XLR connectors, mics with quarter-inch connectors and mics with mini-jack connectors. You got diversity and non-diversity (the former usually has two antennae and typically have fewer dropouts).
Most of you reading this will be using either wireless lav mics or shotgun mics in your productions. Neither is better than the other. As usual, it all depends on the shoot. If the subject needs a lot of mobility (e.g. documentary, wedding, bar/bat mitzvah, etc.), a wireless lav is probably the best way to go. If you’re shooting interviews with each interviewee sitting or standing in the same location, a good shotgun mic set up is nice because then you don’t have to fuss with taking lav mics on and off each person.
Line vs. Mic Level. This relates to the power output of an audio signal. Line level signals are significantly stronger than mic level. Line level signals are what’s needed for musical concerts and the like, so they have preamps to boost the signal level. This is important for the videographer because most of your audio recording devices work at mic level. If you try to get a line level feed into a mic, you will get tremendous distortion, unless you have some kind of device like a direct box that can compensate (if you don’t already have a direct box, aka DI box, as part of your audio arsenal, you should get one). Some digital audio recording devices allow you to adjust the recording level down, and that may help.
Bit Depth and Sample Rates. I am NOT an audio expert. (Nor do I play one on TV). So there’s no way I’m going to pretend to know all the ins and outs of the science of audio. However, as a filmmaker/videographer, you should at least have a modicum of knowledge regarding each.
In short, bit depth is the amount of data recorded in each cycle of audio, which is the sample rate. (And note: it’s bit DEPTH, not RATE. There’s a difference.) Think of bit depth as audio “resolution.” I typically shoot at a 48k/16, that is a 48khz (kilohertz) cycle rate and a 16-bit depth. There is much debate whether it is better to record at 24-bit vs. 16 bit. IMHO, for video (especially if it’s video for the web), you don’t need to significantly increase your audio file size (and required computer processing power) by using a higher bit depth than 16, or a higher sample rate than 48k. That combination has worked fine for me for nearly 11 years.
You Can’t Fix it In Post. If you over or under expose your footage, have too much grain, have terribly shaky camera work, or deal with some other VISUAL hindrance, chances are you can come up with some creative solution to deal with it in post production. (e.g. color grade it a certain way, use b-roll to cover shaky footage, make it black and white if white balance is horrendous, etc.) HOWEVER, if your audio is bad, you are most likely S.O.L. (i.e. in bad shape). There is very little you can do to bad audio to make it sound good. Sure, depending on the issue, sometimes you can add a pass filter here or a compressor filter there to filter out background hum, or boost audio, etc. But 9 times out of 10, you’ll just be stuck with bad audio, which will negatively impact your video. If you have a lot of wind noise because you didn’t use a wind guard, not much you can do. Filming next to a train track with a train noise in the background? Well, you’re stuck with train noise in the background. If you get static interference, or distorted audio from a line level feed going into a mic level receiver with no adjustment, there’s nothing that can fix that. A good photography analogy is shooting in low or medium jpegs and having an image totally blown out. There’s no amount of Photoshopping in the world that create or return information that just isn’t there. Audio is similar. So, do whatever you can to ensure that when you capture audio the first time, you get good, clean audio. I would argue that for once-in-a-lifetime events like weddings, getting good audio is MORE important than getting good video. (Which, by the way, is a great reason for brides to hire a pro vs. Uncle Charlie).
So there you have it. Five facts every filmmaker/videographer should know about audio. Do you have any audio facts and tips you can share? Do so in the comments.
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